/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001-2005 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xerces.internal.utils;

/**
 * This class is duplicated for each JAXP subpackage so keep it in sync.
 * It is package private and therefore is not exposed as part of the JAXP
 * API.
 * <p>
 * This code is designed to implement the JAXP 1.1 spec pluggability
 * feature and is designed to run on JDK version 1.1 and
 * later, and to compile on JDK 1.2 and onward.
 * The code also runs both as part of an unbundled jar file and
 * when bundled as part of the JDK.
 * <p>
 *
 * @version $Id: ObjectFactory.java,v 1.6 2010/04/23 01:44:34 joehw Exp $
 */
public final class ObjectFactory {

  //
  // Constants
  //
  private static final String JAXP_INTERNAL = "com.sun.org.apache";
  private static final String STAX_INTERNAL = "com.sun.xml.internal";

  /**
   * Set to true for debugging
   */
  private static final boolean DEBUG = isDebugEnabled();

  //
  // Private static methods
  //

  /**
   * Returns true if debug has been enabled.
   */
  private static boolean isDebugEnabled() {
    try {
      String val = SecuritySupport.getSystemProperty("xerces.debug");
      // Allow simply setting the prop to turn on debug
      return (val != null && (!"false".equals(val)));
    } catch (SecurityException se) {
    }
    return false;
  } // isDebugEnabled()

  /**
   * Prints a message to standard error if debugging is enabled.
   */
  private static void debugPrintln(String msg) {
    if (DEBUG) {
      System.err.println("XERCES: " + msg);
    }
  } // debugPrintln(String)

  /**
   * Figure out which ClassLoader to use.  For JDK 1.2 and later use
   * the context ClassLoader.
   */
  public static ClassLoader findClassLoader()
      throws ConfigurationError {
    if (System.getSecurityManager() != null) {
      //this will ensure bootclassloader is used
      return null;
    }
    // Figure out which ClassLoader to use for loading the provider
    // class.  If there is a Context ClassLoader then use it.
    ClassLoader context = SecuritySupport.getContextClassLoader();
    ClassLoader system = SecuritySupport.getSystemClassLoader();

    ClassLoader chain = system;
    while (true) {
      if (context == chain) {
        // Assert: we are on JDK 1.1 or we have no Context ClassLoader
        // or any Context ClassLoader in chain of system classloader
        // (including extension ClassLoader) so extend to widest
        // ClassLoader (always look in system ClassLoader if Xerces
        // is in boot/extension/system classpath and in current
        // ClassLoader otherwise); normal classloaders delegate
        // back to system ClassLoader first so this widening doesn't
        // change the fact that context ClassLoader will be consulted
        ClassLoader current = ObjectFactory.class.getClassLoader();

        chain = system;
        while (true) {
          if (current == chain) {
            // Assert: Current ClassLoader in chain of
            // boot/extension/system ClassLoaders
            return system;
          }
          if (chain == null) {
            break;
          }
          chain = SecuritySupport.getParentClassLoader(chain);
        }

        // Assert: Current ClassLoader not in chain of
        // boot/extension/system ClassLoaders
        return current;
      }

      if (chain == null) {
        // boot ClassLoader reached
        break;
      }

      // Check for any extension ClassLoaders in chain up to
      // boot ClassLoader
      chain = SecuritySupport.getParentClassLoader(chain);
    }

    // Assert: Context ClassLoader not in chain of
    // boot/extension/system ClassLoaders
    return context;
  } // findClassLoader():ClassLoader

  /**
   * Create an instance of a class using the same classloader for the ObjectFactory by default
   * or bootclassloader when Security Manager is in place
   */
  public static Object newInstance(String className, boolean doFallback)
      throws ConfigurationError {
    if (System.getSecurityManager() != null) {
      return newInstance(className, null, doFallback);
    } else {
      return newInstance(className,
          findClassLoader(), doFallback);
    }
  }

  /**
   * Create an instance of a class using the specified ClassLoader
   */
  public static Object newInstance(String className, ClassLoader cl,
      boolean doFallback)
      throws ConfigurationError {
    // assert(className != null);
    try {
      Class providerClass = findProviderClass(className, cl, doFallback);
      Object instance = providerClass.newInstance();
      if (DEBUG) {
        debugPrintln("created new instance of " + providerClass +
            " using ClassLoader: " + cl);
      }
      return instance;
    } catch (ClassNotFoundException x) {
      throw new ConfigurationError(
          "Provider " + className + " not found", x);
    } catch (Exception x) {
      throw new ConfigurationError(
          "Provider " + className + " could not be instantiated: " + x,
          x);
    }
  }

  /**
   * Find a Class using the same classloader for the ObjectFactory by default
   * or bootclassloader when Security Manager is in place
   */
  public static Class findProviderClass(String className, boolean doFallback)
      throws ClassNotFoundException, ConfigurationError {
    return findProviderClass(className,
        findClassLoader(), doFallback);
  }

  /**
   * Find a Class using the specified ClassLoader
   */
  public static Class findProviderClass(String className, ClassLoader cl,
      boolean doFallback)
      throws ClassNotFoundException, ConfigurationError {
    //throw security exception if the calling thread is not allowed to access the package
    //restrict the access to package as speicified in java.security policy
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
      if (className.startsWith(JAXP_INTERNAL) ||
          className.startsWith(STAX_INTERNAL)) {
        cl = null;
      } else {
        final int lastDot = className.lastIndexOf(".");
        String packageName = className;
        if (lastDot != -1) {
          packageName = className.substring(0, lastDot);
        }
        security.checkPackageAccess(packageName);
      }
    }
    Class providerClass;
    if (cl == null) {
      //use the bootstrap ClassLoader.
      providerClass = Class.forName(className, false, ObjectFactory.class.getClassLoader());
    } else {
      try {
        providerClass = cl.loadClass(className);
      } catch (ClassNotFoundException x) {
        if (doFallback) {
          // Fall back to current classloader
          ClassLoader current = ObjectFactory.class.getClassLoader();
          if (current == null) {
            providerClass = Class.forName(className);
          } else if (cl != current) {
            cl = current;
            providerClass = cl.loadClass(className);
          } else {
            throw x;
          }
        } else {
          throw x;
        }
      }
    }

    return providerClass;
  }

} // class ObjectFactory
